In a conventional electronic apparatus having an imaging function, such as a digital still camera or a digital video camera, a solid-state imaging device like a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) image sensor is used. A solid-state imaging device has pixels each including a combination of a photodiode that performs photoelectric conversion and transistors, and an image is formed in accordance with pixel signals that are output from the pixels arranged in a two-dimensional fashion.
In recent years, back-illuminated solid-state imaging devices are often used. In a back-illuminated solid-state imaging device, light is emitted onto photodiodes from the back surface side, which is the opposite side from the front surface side on which transistors and wiring layers are stacked on a semiconductor substrate. Back-illuminated solid-state imaging devices are used in compact digital still cameras, cameras for mobile terminals, and the like, and can increase the sensitivity of fine pixels and improve shading characteristics.
For example, a back-illuminated solid-state imaging device can have larger photodiode areas than those in a front-illuminated solid-state imaging device, and characteristically has no wiring layers on the light incident side. Because of these features, a back-illuminated solid-state imaging device can efficiently take incident light into the photodiodes, and achieve excellent sensitivity characteristics. However, a back-illuminated solid-state imaging device takes more reflected light into the photodiodes from the sealing glass surface, an infrared cut filter, the optical system of the camera set, and the like. As a result, flare, ghosts, and color mixing easily occur, and the image quality is degraded. Particularly, in a large-sized solid-state imaging device, the pixel size is large, and the light receiving region is wide. Therefore, the photodiodes take in a large amount of unnecessary light, making the image quality degradation more conspicuous.
To counter this, techniques for preventing unnecessary light from entering photodiodes by providing a light shielding portion between pixels have been developed, as disclosed in Patent Documents 1 and 2, for example.